Introduction

Blue carbon refers to all biologically driven carbon (C) fluxes and storage in the ocean and coastal ecosystems. Blue carbon ecosystems (BCEs) include mangroves, seagrasses, and salt marshes. They play a pivotal role as carbon sinks, storing carbon in their rich organic soils and plant biomass. Despite being smaller than terrestrial forests, they sequester carbon 2-4x more efficiently per unit area. Australia has emerged as a global leader in blue carbon conservation through innovative research, community involvement, and policy integration. However, BCEs in the country face significant threats from coastal development, pollution, and climate change. To safeguard biodiversity and enhance C sequestration potential, coastal ecosystems should be effectively managed. The THRIVE Framework examines critical issues and proposes solutions to promote environmental and sustainable transformations.

Source: Blue Carbon Ecosystems; mangroves, seagrasses, and salt marshes.

What Are Blue Carbon Ecosystems and How Do They Work?

Blue carbon is the term for carbon captured by ocean and coastal ecosystems. BCEs along the coast “capture and hold” C in their plant biomass and predominantly in the soil. The carbon stores in the soil can be up to six meters deep and remain stable for millennia. In addition to C storage, BCEs provide critical ecosystem services that directly benefit biodiversity and human societies. Mangroves offer vital habitats for numerous terrestrial and aquatic species. Further, it stabilises sediments, filters pollutants, and protects shorelines by preventing erosion. They act as natural barriers against storm surges/high-energy waves, safeguarding coastal settlements, and sustaining fisheries, aquaculture, and tourism-based economies.

Tidal marshes, characterised by their deep organic soils and periodic tidal flooding, serve as filters. They improve water quality and provide essential habitats for marine life. Additionally, these marshes help absorb storm energy and mitigate flood damage. Deep-rooted, submerged flowering plants called seagrasses can store up to twice as much carbon per hectare as terrestrial forests, making them extremely efficient carbon sinks. These meadows also protect coastlines, support marine biodiversity, and filter sediments and nutrients.

Source: NOAA Climate.gov

Plants and trees in coastal ecosystems absorb CO₂ through photosynthesis. Some carbon returns to the atmosphere as CH₄ and CO₂, but the rest is buried in sediment. 

The Significance of Blue Carbon Ecosystems

BCEs contribute to 50% of the C sequestered in ocean sediments despite covering less than two per cent of the ocean floor, thus acting as hot spots. Unlike terrestrial forests which eventually become saturated with carbon, the sequestration capacity of coastal ecosystems is more efficient and sustainable. The continuous vertical accumulation of sediment keeps BCEs fresh and capable of holding more carbon, making them potential carbon sinks. These systems can sequester up to 4x more carbon per hectare and store it 30-50x faster than terrestrial forests.

The Paris Agreement urged the urgent limitation of global average temperatures to 1.5 °C; however, studies reveal that they are already 1.54°C above pre-industrial levels. In this scenario, large-scale carbon reduction strategies are essential. One powerful natural solution to combat climate change is through coastal ecosystems’ sequestration and storage of carbon. Furthermore, they locally enhance ocean acidification by absorbing CO₂ for photosynthesis.

Threats to Blue Carbon Ecosystems

Blue carbon faces severe threats from climate change, deforestation, rising sea levels, and human development. It has catastrophic effects as the destruction of carbon sinks leads to the release of stored carbon as CO₂ and methane (CH₄). Australia has already lost half of the coastal ecosystems since European colonisation (~25,000 km² of salt marshes and mangroves, and 32,000 km² of seagrasses) owing to human activities and natural disasters. Each year coastal developments contribute to additional losses, as well as adding to stressors such as heat waves and extreme weather events. Australia’s potential CO₂ emissions from the loss of blue carbon are estimated at 2.1–3.1 million metric tons of CO₂ equivalent per year. It is worth considering that the current global CO₂ emission is estimated to be 37.01 billion metric tons. 

A 2021 study revealed that bottom trawling globally releases 1 billion metric tons of CO₂ from seabed sediments into seawater annually, equivalent to the annual emissions of the global aviation industry. While seawater absorbs a large portion of this CO₂, it is estimated through models that up to 370 million metric tons could be released into the atmosphere each year. Trawl fishing on the seabed contributes around 25% of Australia’s wild seafood catch. Thus, it is crucial to recognise the value of “blue carbon” accumulated over centuries, and its vulnerability to unsustainable practices, to mitigate climate change. Furthermore, greening the fishing industry and aquaculture can convert these negative impacts into positive ways of sequestering more carbon.

To develop such mitigation strategies, reliable methods for measuring blue carbon sinks are essential. Integrating field data with variables such as ecosystem mapping, helps to understand the spatial extent of these ecosystems.

The Status of Blue Carbon Ecosystems in Australia

Australia has some of the world’s largest blue carbon storage capacity, with 5–11% of global blue carbon soil stocks and 2–7% of annual soil carbon sequestration. The country harbours about 12% of the World’s blue carbon ecosystems. Notably, the seagrass meadows in the Great Barrier Reef alone host an estimated 11% of the world’s seagrass blue carbon. In Australia, Queensland is home to half of the country’s blue carbon.

Source: Serrano et al., 2019

The Distribution of climate regions in Australia, as well as the spatial distribution of tidal marsh, mangrove, and seagrass ecosystems.

A study by Serrano et al., 2019 evaluated the distribution of blue carbon in different climatic regions of Australia. Mangroves and tidal marshes are mostly found in tropical regions, while seagrasses span tropical, subtropical, and arid areas. The ability of these BCEs to sequester C depends on their coverage and the climatic region in which they are located. However, knowledge of the extent of Australian blue carbon is incomplete owing to challenges in mapping these ecosystems. Importantly, the extent of seagrasses and tidal marshes may be significantly larger than currently estimated.

Strategies for Conservation and Restoration

Wetlands Australia 31 is the Australian government’s initiative for blue carbon. The country is pursuing greater recognition and protection of coastal blue carbon ecosystems through the International Partnership for Blue Carbon, The Ramsar Convention, and by supporting projects under the National Environmental Science Program (NESP). Marine Protected Areas (MPAs) have proven to be efficient at achieving marine conservation goals as they control human interference, depending on the activities permitted in a particular reserve. In Australia, BCEs are now largely protected within World Heritage Sites and Ramsar-listed wetlands, safeguarding biodiversity and cultural values.

Similarly, projects funded by DEECA conduct assessments to map blue carbon opportunities. The project identified around 500km2 of land amenable to restoration through various management activities. AirSeed: an initiative to plant up to 40,000 seed pods per day using drones in remote and inaccessible areas contributes to restoring mangroves. The country’s Aboriginal Corporations have significantly contributed to the restoration of BCEs by planting mangrove seedlings using their refined knowledge of mangrove husbandry and active restoration methods.

Australia is one of a few countries that has voluntarily reported human-induced greenhouse gas emissions and carbon sequestration associated with coastal wetlands in the National Greenhouse Gas Inventory. Australia is also planning its first national ocean ecosystem account, focusing on coastal blue carbon ecosystems. This work will provide information on the extent and condition of the ecosystem, as well as ecosystem services such as coastal protection and carbon sequestration. As part of the Emission Reduction Fund, the country is developing a method to secure carbon credits to restore BCEs from the reintroduction of tidal flows.

Conclusion & Call to Action (CTA)

Efforts to conserve and restore blue carbon ecosystems not only prevent emissions and conserve biodiversity but also enhance their capacity to sequester carbon, making them an essential part of global climate change mitigation strategies. Recognising their value through policies, sustainable management, and financial incentives can significantly reduce emissions and safeguard critical ecosystems. The NSW Blue Carbon Strategy 2022-2027, identifies 5 overarching priorities and the actions we should deliver over the next 5 years.

• Conserve blue carbon ecosystems and support their adaptation and migration.
• Deliver blue carbon projects on public, private, and First Nations people-owned and managed land.
• Embed blue carbon in coastal and marine policy planning and management.
• Progress in blue carbon research.
• Promote pathways for blue carbon investment.

With a focus on ensuring the ‘thrivability‘ of all species on earth, we can work together to explore nature-based solutions for a future beyond sustainability.

Applying the THRIVE Framework to Blue Carbon Ecosystem Management

Restoring blue carbon as a nature-based solution utilises its natural resilience and ecological functions to reduce the impacts of climate change, promote biodiversity, address coastal hazards, and encourage sustainable development. These ecosystems require much greater attention than they have received thus far as a means of securing humanity’s future health and well-being. Through The THRIVE Framework, the THRIVE Project investigates key issues and opportunities. Thus, THRIVE encourages individuals to take action by raising awareness, advocating for conservation policies, and reducing their carbon footprint to improve thrivability in coastal ecosystems. THRIVE offers insights that promote environmental and social sustainability systemically and holistically, without compromising them.

The following foundational focus factors—science-based targets, strong sustainability, finite resources, and value-based innovation—are central to its mission. By integrating these principles, THRIVE promotes systemic change that balances ecological health with human development. The project leverages scientific research, innovation, and strategic collaboration to address environmental challenges while ensuring ethical and sustainable resource management. These principles guide the development of solutions that protect and restore blue carbon ecosystems, securing long-term benefits for both nature and society.

To support these ideals, engage with THRIVE’s clusters and resources, including podcasts, webinars, whitepapers, and the blog. Advocate for thrivability by supporting aligned organisations and leaders prioritising sustainable futures. Stay informed via our website and LinkedIn for updates.